SYMPOSIA PAPER Published: 01 January 1975

Effects of Environment on the Fatigue of Graphite-Epoxy Composites


Torsional and flexural fatigue tests were performed on both uniaxial (0°) and crossplied (±45°) graphite-epoxy materials at temperatures of 24 and 7°C in environments of air and water. The results of the torsion testing showed that the number of cycles required to cause an initial decrease in stiffness as well as the rate of stiffness loss was a function of temperature and environment; the most significant losses were noted for tests at the higher temperature in water. The torsional fatigue specimens were subsequently tested in four-point bending to determine the effect of torsional damage on longitudinal properties. This damage caused changes in the flexural stiffness, failure stress, and failure energy, depending on the stress and environmental histories. The flexural fatigue tests also showed a significant effect of water (at 24°C) on the material behavior. These results are compared with the results of previous investigations and are discussed in terms of proposed damage mechanisms.

Author Information

Sumsion, HT
Ames Research Center, NASA, Moffett Field, Calif.
Williams, DP
Ames Research Center, NASA, Moffett Field, Calif.
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Developed by Committee: E08
Pages: 226–247
DOI: 10.1520/STP33175S
ISBN-EB: 978-0-8031-4652-5
ISBN-13: 978-0-8031-0346-7